Elaborasi Karakteristik Edible Film dari Gelatin Mamalia dan Ikan: Kajian Meta-analisis

Abstract

Penggunaan edible film sebagai kemasan makanan sampai saat ini masih terus dikembangkan karena salah satu sifatnya yang mudah diurai. Edible film yang terbuat dari protein seperti gelatin memiliki sifat mekanik dan fisik yang baik. Secara umum, gelatin terbuat dari mamalia seperti sapi dan babi. Namun, karena adanya isu keagamaan dan kesehatan, gelatin dari sumber hewan lain seperti ikan terus dikembangkan. Perbedaan gelatin mamalia dan gelatin ikan yang digunakan tentu berpengaruh signifikan terhadap karakteristik edible film yang dihasilkan. Namun, terdapat hasil penelitian individu yang berbeda yang menyatakan tidak ada perbedaan signifikan antara edible film gelatin mamalia dan edible film gelatin ikan dalam hal kekuatan tarik dan permeabilitas uap air. Oleh karena itu, perlu dilakukan studi meta-analisis dengan tujuan untuk mendapatkan kesimpulan yang valid.

Penelitian ini dilakukan dengan 6 tahapan yaitu perumusan pertanyaan penelitian, penentuan kriteria inklusi dan eksklusi, pencarian dan pengumpulan sumber studi, ekstraksi data, pengolahan data, dan interpretasi hasil meta-analisis. Metode meta-analisis yang digunakan sebagai effect size (ukuran efek) adalah Standardized Mean Difference (SMD) yang berupa Hedges’ d. Adapun perangkat lunak yang digunakan untuk penelitian meta-analisis yaitu Microsoft Excel 2016, Meta-Essential tools, Web Plot Digitizer, dan SPSS16.

Pencarian dan pengumpulan sumber studi dilakukan di 11 database berupa Science Direct, Google Scholar, Wiley Online Library, Proquest, ACS Publication, Taylor & Francis Online, Pubmed, Nature, Springer, EBSCO, dan Garuda Ristekbrin. Didapatkan total 1.790 artikel yang kemudian diseleksi duplikasi sebanyak 668 artikel sehingga tersisa 1.122 studi. Setelah dilakukan penyeleksian berdasarkan judul dan abstrak, diperoleh 48 artikel lengkap untuk dikaji. Selanjutnya sebanyak 42 artikel tersisih karena tidak relevan dan tidak memiliki data yang lengkap hingga tersisa 6 artikel terpilih yang digunakan untuk meta-analisis. Hasil meta-analisis disajikan dalam bentuk forest plot, funnel plot, analisis subgrup, dan meta-regresi.

Terdapat 5 parameter yang dianalisis pada penelitian ini yaitu kekuatan tarik, elongasi, modulus elastisitas, permeabilitas uap air, dan transparansi. Nilai (ukuran efek (95% CI), nilai p, effect magnitude, nilai heterogenitas, dan bias publikasi) pada masing-masing parameter secara berturut-turut adalah (-1.72 (-2.67 s.d. -0.76), p < 0.001, efek besar, heterogenitas cukup tinggi (72.98%), tidak terdapat bias publikasi); (0.01 (-1.04 s.d. 1.06); p = 0.493, efek kecil, heterogenitas cukup tinggi (72.08%), bias publikasi moderat); (-1.11 (-1.39 s.d. -0.83), p < 0.001, efek besar, heterogenitas rendah (0.00%), tidak ada bias publikasi); (-1.48 (-2.30 s.d. -0.66), p < 0.001, efek besar, heterogenitas cukup tinggi (68.14%), tidak ada bias publikasi); (-1.33 (-1.83 s.d. -0.84), p < 0.001, efek besar, heterogenitas 0.00%, tidak terdapat bias publikasi).

Analisis subgrup juga dilakukan yaitu berdasarkan metode pembuatan edible film yang digunakan. Hasil analisis menunjukkan bahwa perbedaan metode pembuatan edible film berpengaruh signifikan terhadap karakteristik kekuatan tarik (p-between = 0.006) dan elongasi (p-between = 0.001). Selain itu, terdapat faktor tambahan lain yang dapat mempengaruhi hasil analisis yaitu konsentrasi gelatin yang diuji dengan meta-regresi. Hasil meta-regresi menggambarkan bahwa terdapat pengaruh signifikan dari perbedaan konsentrasi gelatin terhadap karakteristik kekuatan tarik (p = 0.04), elongasi (p = 0.01), dan permeabilitas uap air (p = 0.01).

Berdasarkan hasil meta-analisis, dapat disimpulkan bahwa terdapat perbedaan karakteristik fisik (kekuatan tarik dan modulus elastisitas) dan mekanis (permeabilitas uap air dan transparansi) yang signifikan antara edible film gelatin mamalia dengan edible film gelatin ikan. Film yang terbuat dari gelatin mamalia memiliki sifat mekanik yang lebih baik. Namun, edible film yang terbuat dari gelatin ikan bersifat lebih baik dalam menahan uap air. Kemudian terdapat faktor lain yang dapat mempengaruhi karakteristik fisik dan mekanis edible film seperti metode pembuatan film dan konsentrasi gelatin yang digunakan.

Edible films (EF) are continuously developed as food packaging alternatives due to their biodegradable properties. Edible films can be made from proteins such as gelatin. In general, gelatin is made from mammalian such as bovine and porcine. However, due to religious and health issues, gelatin from other animal sources such as fish continues to be developed. Past studies described that there were significantly different properties between mammalian gelatin film and fish gelatin film. Some studies reported that mammalian gelatin films are significantly different from fish gelatin films. However, there have been different results among individual studies. Therefore, the present study would like to obtain a valid conclusion across different studies using a meta-analysis approach. This research was conducted in 6 stages, i.e., formulation of the research question, study selection (inclusion and exclusion criteria), literature search, data selection, data synthesis, and interpretation of meta-analysis results. The Meta-analysis method used as the effect size is the Standardized Mean Difference (SMD) or Hedges' d. The software used for meta-analysis was Microsoft Excel 2016, Meta-Essential tools, Web Plot Digitizer, and SPSS16. A literature search was carried out by using 11 databases i.e., Science Direct, Google Scholar, Wiley Online Library, Proquest, ACS Publication, Taylor & Francis Online, Pubmed, Nature, Springer, EBSCO, and Garuda Ristekbrin. The initial searches resulted in 1.790 articles and as many as 668 references were eliminated because its duplicate. After selecting based on the title and abstract, 48 complete articles were obtained for the review process. Furthermore, as many as 42 articles were excluded because they were irrelevant and had insufficient data. As a result, 6 selected articles were used for meta-analysis. The results of the meta-analysis are presented using forest plots, funnel plots, subgroup analysis, and meta-regressions. There were 5 parameters analyzed in this study, i.e., tensile strength, elongation at break, elastic modulus, water vapor permeability, and transparency. The effect size (95% CI), p-value, effect magnitude, heterogeneity, publication bias respectively in each parameter were -1.72 (-2.67 to -0.76), p < 0.001, large effect, quite high heterogeneity (72.98%), no publication bias; 0.01 (-1.04 to 1.06), p = 0.493, small effect, moderately high heterogeneity (72.08%), moderate publication bias; -1.11 (-1.39 to -0.83), p < 0.001, large effect, low heterogeneity (0.00%), no publication bias; -1.48 (-2.30 to -0.66), p < 0.001, large effect, moderately high heterogeneity (68.14%), no publication bias; and -1.33 (-1.83 to -0.84), p < 0.001, large effect, 0.00% heterogeneity, no publication bias. Subgroup analysis was also conducted based on the film fabrication method. The results showed that different methods significantly affect the characteristics of the tensile strength (p-between = 0.006) and elongation at break (p-between = 0.001). Furthermore, there was an additional factor called the concentration of gelatin that might affect the analysis results. Hence, meta-regression was also conducted in this study. The results of meta-regression illustrate that there was a significant effect of gelatin concentration on the characteristics of tensile strength (p = 0.04), elongation at break (p = 0.01), and water vapor permeability (p = 0.01). In conclusion, there are significant differences (p < 0.05) in physical characteristics (tensile strength and modulus of elasticity) and mechanical (water vapor permeability and transparency) between mammalian gelatin films and fish gelatin films. Mammalian gelatin films have better mechanical properties. However, fish gelatin films are better at retaining water vapor. Besides, it is necessary to give attention to additional factors that can affect the physical and mechanical characteristics of edible films such as the method of making the film and the concentration of gelatin used.